This project represents the first part of a program designed to search for the presence of primary aging processes and the natural means by which longevity evolved during the recent evolutionary history of man. A brief review of the general objectives and rationale of this program is presented. Present work is focused on possible age-dependent relaxation of specific genes in tissues where their expression is not expected. Evidence has been found for an age-dependent expression of alpha and beta globin genes in liver and brain tissues in the long-lived C57BL/6J mouse strain; whereas in the short-lived AKR mouse strain, having a high incidence frequency of leukemia, an early expression is found only in the thymus, and this is limited to the C-type virus genes. More recent work has now extended this investigation to include casein, alpha-fetal protein and mouse mammary tumor virus genes.